Hygrometer



March 3l, 1936. D. P. WICKERSHAM ET AL 2,035,932

HYGROMETER Original Filed Nov. 23", 1952 INVENToR/ ai M am m #4ATTORNEYS Patented Mar. 3l, 1936 UNITED STATES PATENT OFFICE HYGROMETERtion of Ohio Application November 23, 1932, Serial No. 644,086 RenewedSeptember 4, 1935 10 Claims.

'I'his invention relates to improvements in hygrometers, it moreparticularly relating to that class of hygrometers in which the moistureresponsive element is formed of wood or similar brous material,

One of the objects of the invention is to provide a hygrometer of thetype referred to which will be simple in construction and effective inoperation.

Another object of the invention is to provide a librous moistureabsorbing hygroscopic element so constructed as to shorten the bers ofthe element to a degree to reduce the time lag in producing humidityindications, but at the same time have imparted to the element therequisite strength to perform the work required in actuating theindicating devices.

Another object is the provision of an improved form of brous hygroscopicelement of laminated construction, the laminations of which are arrangedso as to eliminate any tendency of the element to warp or buckle whenexpanding.

Another object is the provision of an adjustable, yieldable supportingmeans for the moisture responsive element whereby damage to the workingparts of the instrument is averted in the event of the element becomingsaturated with moisture to an extent to cause it to expand beyond anormal limit.

Other objects of the invention will appear from the accompanyingdescription.

In the accompanying drawing:

Fig. 1 is a perspective view of the improved hygrometer with a portionof the outer casing broken away so as to show the interior construction.

Fig. 2 is a top plan View also with a portion of the outer casing brokenaway.

Fig. 3 is a vertical section on the line 3 3 of 40 Fig. 2.

Fig. 4 is an enlarged transverse section on the lined-4 of Fig. 3.

Fig. 5 is a further enlarged fragmentary vertical section on the line 55 of Fig. 3.

45 v Fig. 6 is a fragmentary perspective view of an assembly composed oftwo details of the device.

A large number and variety of materials are hygroscopic, and inpractically all instances each v material is affected to a degreedirectly propor- 50 tional to the degree of moisture carried by the air.The eiiect of vapor on wood is well known, a body formed of woodexpanding in all directions whereby its length, breadth and thickness isincreased by the absorption of atmospheric 55 vapor. Wood in the form ofa plank expands most noticeably in the direction of its width, and 4 thygroscopic elements have been made in the past to utilize thiscomparatively great expansion by forming elements from planks by simplysawing a comparatively short section from the end of a plank. 'Ihe widthdimension of the plank now corresponds to the length dimension of theelement, and the element is usually supported at one end While it isconnected at the other end to some means of indication.

One of the disadvantages of this type of moisture responsive element isthat the element follows the tendency of the plank in expansion, thatis, if any portion of a plank is inclined to bow in one direction or theother, an element removed rom that portion of the plank would also showa tendency to bow, or perhaps buckle. In other words, elements havingthe original undisturbed grain of the plank, may or may not expand inthe straight line desired, and if only those portions of a plank areselected which do not show a tendency to bow or buckle, themanufacturing cost of the instrument is increased.

The improved element is a laminated structure, composed of a pluralityof small sections cemented together, the end grain of each of thesections being disposed as in the case of the simple element cut fromthe end of the plank, that is, at right angles to the length dimensionof the element.

Referring to the drawing, the improved element is indicated in generalat I, the several sections at 2 and the joints between them at 3.

A simple and preferred method of building up these improved elements isas follows: A plank is sawed lengthwise into strips and alternate stripsare inverted side for side and reassembled with cemented joints wherebya laminated plank whose width is equal to the length dimension desiredfor the elements, with the bers extending in the same direction, butsome of which have been inverted end for end with relation to theothers, is obtained, after which the elements are sawed from the end ofthis laminated plank. There is thus formed an improved woodenhygroscopic element which has lost none of the advantage of the simpleelement, but has the further advantage that the improved element expandsin the desired straight line, which may be explained as follows: If aportion of the original plank had a tendency to bow in any directionduring expansion, each alternate strip after inversion in retaining itstendency to bow corrects the initial tendency of the uninverted stripsby introducing an equal bow in the opposite direction, with the resultthat an element is obtained which will expand in the general straightline desired. On the other hand, if there was no tendency to bow in theoriginal plank, no tendency to bow is introduced, since there was nodeviation to correct.

Hygrometers are sensitive according to the sen'f sitivity of theelement. The sensitivity of the element when formed of iibrous material,such as wood, may be increased by shortening the fibers, which amountsto decreasing the vapor penetration distance so that vapor entering froma side does not have far to penetrate before meeting vapor entering froman opposite side. Shortening of the penetration distance may be broughtabout by decreasing the cross-sectional area, but the probable resultwould be that the element would not have suflicient strength to actuatea suitable indicating device. Therefore we have adopted a comparativelylarge H-cross-section for the greater portion of the body of theelement, as bestseen in Fig. 4, whereby we not only obtain an element ofample strength, but also an element having a high degree of sensitivity.Sensitivity is obtained by milling a deep groove 4 into each of the twoopposite Sides 5 and 5 of the element, the grooves 4 extendingsubstantially from end to end of the element thereby shortening thegreater percentage of the long fibers. In the other two sides 6 and 6shallower grooves 1 are milled which decrease the length of most of theremaining long fibers, the grooves 1 extending throughout the length ofthe element. The latter grooves 'I are also employed for another purposeas will now be explained.

The moisture responsive element actuates an arm 8 which is provided witha pointer 9. The

arm is pivotally mounted on a hinge pin I0 secured in upstanding ears IIattached to an outturned portion I2 of a back-plate I3. The arm isprovided with a longitudinal slot extending from a connecting portion Id at the upper end of the arm to the lower end, leaving the lower endopen, so that the element I may be slid into the arm, the legs I5 of thearm being slidably fitted in the shallow grooves 'I previouslymentioned. 'Ihe inner edges of the legs I5 are outturned as shown at I6(Figs. 4 and 6) to strengthen the arm and form guiding flanges for theelement. The lower end of the arm is connected by a member 8 soldered orsecured in any suitable manner to the bent portions" which receive thehinge pin IIJ.

Each end of the element I is protected against abrasion by a small metalpad, there being a pad I'I secured to the upper end of the element wherecontact is made with the lower edge of the connecting portion I4, and aVsecond pad I8 secured to the lower end where the element makes con-Ytact with the yieldable supporting means which will now be described. l

In eiect the arm 8 is partly supported by the element I and follows theexpansion and contraction thereof, the arm being returned as the elementcontracts by a return spring I9 (Fig. l) In turn the element I issupported on members attached to the out-turned portion I2 of the backplate and located at one side of the pivotal mounting of the arm 8. Inthe present instance, the element supporting means is both adjustableand yieldable, the adjustable feature being provided to compensate forthe small differences encountered in the manufacture of the moistureresponsive elements, while the advantage of the yieldable feature willappear later.

In View of the pivotal mounting of the arm 8 and the disposition of theelement supporting means, as seen in Figs. l and 5, it shoud be clearthat upon expansion of the element I the arm will be moved to the rightabout the pivot pin I9 and that a reverse movement of the arm will takeplace when the element is giving up its moisture and contracting. InFig. 5 the arm is shown at a slightly different angle than is shown inFig. 1 or Fig. 3. One end of the spring I9 is hooked to a small bar 2lheld in the notched lingers 22 of the arm, while the lower end of thespring is secured to a spring post 23 xed to the out-turned member I2.

The purpose of the yieldable support is as follows: The hygrometer scaleshould be extended so as to indicate saturation at one end and a verydry condition at the other. In the present device the saturation pointis obviously at the right end of the scale, since the arm 8 swings inthat direction during expansion. There would be no point in allowing thepointer 9 to swing further than the saturation designation, therefore astop-pin 24 is secured to the back-plate I3 at the proper place toprevent an over-swing of the arm beyond the end of the scale. Thus thepointer will swing to the saturation point when the air reaches thatcondition, but should the element become water soaked from any cause,the added expansion thereof will be expended in forcing down aspring-pressed plunger 25 which forms a part of the supporting means.

The plunger 25 is slidably fitted and retained in the bore 26 of athimble 2'I which is exteriorly threaded for insertion in an interiorlythreaded boss 28 secured to the out-turned member I2, the location beingsuch that the supporting means is on the opposite side of the arm centerfrom the hingeable connection of the arm with the member I2. A plungerspring 29 is interposed between the plunger and a plate 30 fixed in thelower portion of the thimble 21. The power of the spring 29 should besomewhat greater than the power of the return spring I9, so that theplunger will be forced from its normal upper position only in the eventthe element becomes water soaked.

The present scale 3I is calibrated to read in percentages of relativehumidity of the air, therefore the extreme right hand end is designatedor saturation, while the left hand end denotes a very dry air condition,intermediate points being struck off at proper intervals. The scale ismounted in any suitable manner on the outer surface of an extendedmember 32 secured to the back plate I3 in proximity to the pointer 9.

The working parts of the instrument are protected by an outer casing 33removably secured to the back-plate I3, and in the walls of the outercasing are numerous openings 34 to provide free access to the air.

By the foregoing description it will be seen that we have provided asimple, inexpensive and eilicient instrument for noting'the variationsofthe air as regards the relative humidity thereof, having a hygroscopicelement of sufciently large cross-sectional area whereby ample power isderived for actuating the indicating means or a simple form of humiditycontrol device, yet with the cross-sectional area so distributed thatthe greater portion of the bers are short and the penetration distanceis therefore also shortened, resulting in reducing the time lag of theinstrument both during a condition of a rising percent# age of relativehumidity and. in a fall thereof.

Having thus described our invention we claim:

1. The method of forming a hygroscopic element consisting in severing awooden plank lengthwise into a plurality of strips, inverting some ofsaid strips side for side, forming from the strips a laminated plank,and severing crosswise from said plank a piece to form a hygroscopicelement, the length of which is represented by the width of the plankand whose bers extend at right-angles to the length thereof.

2. The method of forming a hygroscopic element consisting in severing awooden plank lengthwise into a plurality of strips, inverting some ofsaid strips side for side, forming from the strips a laminated plank,and severing crosswise from said plank a piece to form a hygroscopicelement, the length of which is represented by the width of the plankand whose bers extend at right-angles to the length thereof, and forminggrooves in the sides of said severed piece extending in the direction ofthe length thereof to decrease the length of the fibers.

3. The method of forming a hygroscopic ele ment consisting in severing aplank lengthwise into a plurality of strips, inverting alternate stripsside for side, cementing the strips together to form a laminated plank,severing crosswise from the laminated plank portions thereof, the lengthof each of which is represented by the width of the plank and whosefibers extend at right-angles to the length thereof.

4. The method of forming a hygroscopic element consisting in severing aplank lengthwise into a plurality of strips, inverting alternate stripsside for side, cementing the strips together to form a laminated plank,severing cross-wise from the laminated plank portions thereof, thelength of each of which is represented by the width of the plank andwhose bers extend at right-angles to the length thereof, and groovingthe severed portion lengthwise to reduce the length of the fibers.

5. A hygroscopic element formed of laminated wood with the bers of thelaminations all extending at right-angles to the length of the element,said element having grooves extending throughout the length thereof toreduce the length of the fibers without materially decreasing thestrength of the element.

6. A hygroscopic element formed of laminated wood with the fibers of thelaminations all extending at right-angles to the length of the element,each laminated portion extending entirely across the width of theelement, said element having grooves extending throughout the lengththereof to reduce the length of the fibres without materially decreasingthe strength of the element.

'7. In a hygrometer, an upwardly extending arm having a lower offsetportion, a support to which said o'set portion is pivotally connected,an elongated expansible and contractible moisture responsive elementmovably mounted in said arm having its upper end engaging a part of saidarm, and a second support for the lower end of said arm removed from thepivotal point of said arm.

8. In a hygrometer, an upwardly extending arm having an elongatedrecess, an offset portion on the lower end of said arm, a support towhich said offset portion is pivotally connected, an elongatedexpansible and contractible moisture responsive element mounted in therecess of said arm and having grooves to receive portions of said arm toslidably connect the element and arm, the upper end of said elementhaving an engagement with a part of said arm, and a second support forthe lower end of said element removed from the pivotal point of saidarm.

9. The method of forming a hygroscopic element consisting in severing aplurality of strips of wood lengthwise, inverting at least some of saidstrips side by side to form from the strips a laminated plank, unitingsuch inverted strips together, and severing cross-wise from said plank apiece to form a hygroscopic element whose fibers extend at right-anglesto the length thereof.

10. The method of forming a hygroscopic element consisting in severing aplurality of strips of wood length-wise, inverting at least some of saidstrips side by side to form from the strips a laminated plank, unitingsuch inverted strips together, severing cross-wise from said plank apiece to form a hygroscopic element whose bers extend at right-angles tothe length thereof, and forming grooves in the sides of said severedpiece extending in the direction of the length thereof to decrease thelength of the fibers.

DON P. WICKERSHAM. KARL OTTO WALDVOGEL.

